1. Field of the Invention
The present invention relates to a camera which has a zoom lens or to which a zoom lens is attachable, and in particular to enlarging a visual field of a finder as compared with real photographing range and a focus detecting area in the abovementioned camera.
2. Description of the Prior Art
In a camera, enlarging a visual field of a finder as compared with real photographing range is preferable because a position of an object (especially a moving object) can be observed before the object comes into the real photographing range.
However, in a conventional single lens reflux camera, the photographing range approximately corresponds to the visual field of its finder, therefore the finder coverage (visual field of finder/photographing range) is usually 90% to 100%. This is because, with the finder coverage being enlarged, the finder optical system becomes large to fail in obtaining a small-sized camera, and further, the performance of a photo-taking lens is not assured outside the photographing range.
There are many cases in which information of an object outside the photographing range field are required. For example, a composition of a photographic scene is determined based on the information and a photographer is on stand by to take a picture before a moving object comes into the photographing range and is waiting for a shutter release opportunity.
Further, if the focus detecting area is enlarged, focus detection can be achieved even if the main object gets out of the center of the photographing scene, so that a composition can be selected more freely and it is advantageous for a photographer.
However, in order to enlarge the focus detecting area, usually a focus detecting module comprising a focus detecting optical system, a light receiving element, for example, a CCD line sensor has necessarily to be also large-sized, which makes it difficult to obtain a camera having a preferable compact structure and design.
In this connection, the applicant of this invention has proposed in U.S. patent application Ser. No. 389,908 that at the focus detecting time, the focus detecting area is enlarged by setting the focal length of a photo-taking lens at the shortest end. However, in this preceding application, the focal length returns from the shortest end to the former focal length by manual operation of a photographer, and further, the relation between the focus detecting areas at the times of finder observation and photographing respectively is not referred to, so that it is difficult to grasp the relation between the visual field of the finder and the real photographing range when the focal length of the photo-taking lens is at the shortest end.